Dry rectifier



April 25, 1939. o. GElsLER ET Ax.

DRY RECTIFIER Filed July 24, 1957 Patented Apr. 25, 1939 UNITED KSTATESOttmar Geisler andHeinrich Herrmann, Nuremburg, Germany, assignors toSddeutsche Apparate-Fabrik G. m. b. H., Nuremburg, Germany ApplicationJuly 24, 1937, Serial No.

In Germany August 3, 1936 4 claims. (cl. irs- 366) Metal dry rectiflersare known whose effective area is very small. They are employed ifrectiers .of greater areas are not suitable,on account of theircomparatively high self-capacity, or if very small currents of highvoltage are to be rectified.

It is well known to produce rectifier discs or units, which in mostcases are assembled in an insulating tube, by punching them out from aplate provided with the rectifying semi-conductor ayer.

Rectiflers as provided by the invention are likewise manufactured inthis way, but have certain advantages over the known devices, as will beunderstood from the following description, reference being had to theaccompanying drawing in which Y Fig.,l Vis a partially sectioned view,drawn to a much enlarged scale, of a rectifier according to theinvention and also shows the wiring diagram of a circuit therefor. Fig.2 represents a section on line 2-2 of Fig. 1.r Fig. 3, drawn to. a stilllarger scale, is a side view of part of a plate from which the rectifierunits are cut by punching.

As shown in Fig. 1 the rectifier chosen as one example comprises threeunits A which each consist of a metal disc I, a semi-conductor layer 2and three metal projections 3 provided on layer 2. The projections 3 ofthe unit A shown on the left in Fig. 1 are bearing against the disc I ofthe middle unit A, whose projections 3 in their turn rest against thedisc I of the unit A represented on the right in Fig. l. The projections'3' of this third unit A bear against a metal cap 4 arranged to close acylindrical casing 5 at one end thereof.

A second such cap, 6, is disposed on the other endk of the casing 5. Thecaps 4, 6 may be held on casing 5 by frictional contact or may befastened thereto by a cement free of water, or may be4 secured on casing5 in any other suitable manner. Casing 5 is of an insulating materialthat may be a high melting glass, and contains the units A. Located inthe casing 5 is also a helical spring I disposed between cap 6 and theunits A. Spring 1 causes the projections 3 and discs yI to bear with thenecessary contact pressure against each other and also affords thelcontact pressure necessary between cap 4 and those projections 3 whichare ing an oblique position and thus contacting with each other at theiredges, causing short-circuits to occur in this way. In the knownarrangements 'these short-circuits can occur because the units thereofhave only one such projection, thus failing to support each other. Thesupporting action provided by the invention will -be most perfect if theprojections 3 are arranged in symmetrical distribution.

In this way rectiiiers have been manufactured which are adapted forseveral 1000 volts with some milliamperes load.

Instead of providing three imits A, as shown', any suitable or desirednumber thereof may be assembled. Furthermore rectifier's comprising 15units of the novel construction may be included in circuits differentfrom that represented in Fig. 1 by way of example. In order to adapt therectiiiers for circuit arrangements of a certain well -knownkind,contact discs fitted with solderin tabs may be disposed between theunits A.

Rectifiers of the construction here disclosed may be comprised inAcircuit arrangements of the kind known as AGraetz connection.

The units A, which as described consist; of the parts I, 2, 3, are inaccordance with the invention manufactured as follows.

To a metal plate I, Fig. 3, forinstance an iron plate, a semi-conductorvlayer 2, consisting inwell known manner of selenium or cuprous oxide,for 30 instance, is applied by melting or is produced thereon in anysuitable way and then is made to undergo thermal or other influences, asmay be necessary. On this layer the metallic projections 3 are formed byany one of the well known proc- 35 esses usually employed for formingrectifier counter-electrodes, for example, by die-casting, and they areproduced in groups each of which at least comprises three suchprojections arranged in triangular relation, as shown in Fig. 2. 'I'hebody thus obtained is coated with a varnish. The coat'of varnish isdesignated I2. From this blank discs of the desired size, having adiameter of 8 to 9 millimetres, for instance, and carrying a group ofthe projections 3, are cut by punching.

The coat of varnish I2 prevents the semi-conductor layers 2 from beinginjured at vtheir edges by this punching operation. However this coat isso thin as to be removed from the projections 3 when assembling theunits A, parts 3 and I or 4 50 thus being caused to make metalliccontact with each other.

What is claimed is:

1. A method of manufacturing dry-rectifier units which consists inapplying a senil-conductorl 55 layer to a metal plate', then providingthis layer 3. A method according to claim 1, which comwith metalprojections arranged in groups, and prises coating the said blank with avarnish. nally cutting the blank formed of such plate, 4. A methodaccording to claim 1, which comlayer and metal projections, into'portions each prises arranging the metal projections of each comprisingone of these groups. p group in symmetrical relation to each other.

2. A method according to claim 1, in which the OTTMAR GEISLER. metalprojections are produced by die-casting. HEINRICH HERRMANN.

